Multiple tier horizontal diaphragm cells

ABSTRACT

A multiple tier horizontal diaphragm cell series having a top anode compartment, a bottom cathode compartment and a plurality of intermediate cell units for electrolyzing alkali metal chloride solutions. An impervious partition divides the intermediate cell units into an upper cathode compartment containing an ion-permeable diaphragm supported by the cathode, and a lower anode compartment. The cathode compartments and the anode compartments have different outlets for the gaseous products and liquids removed from each compartment.

United States Patent 1 1 v Barnabe Nov. 6, 1973 OUTLET MULTIPLE TIER HORIZONTAL DIAPHRAGM CELLS Charles E. Barnabe, Westport, Conn.

Inventor:

Assignee: Olin Corporation, New Haven,

Conn.

Filed: Nov. 24, 1971 Appl. N6; 201,888

0.5. Ci 204/256, 204/98, 204/254 Int. Cl B01k 3/10 Field 61 Search 204/98, 254, 255,

References Cited 7 UNITED STATES PATENTS I 5/1933 Hunter 204/256 BR/NE Na O 2/1966 Beer 204/98 Primary Examiner-John H. Mack Assistant Examiner-W. l. Solomon Attorney-Gordon D. Byrkit et al.

[ 57] ABSTRACT A multiple tier horizontal diaphragm cell series having a top anode compartment, a bottom cathode compartment and a plurality of intermediate cell units-for electrolyzing alkali metal chloride solutions. An impervious partition divides the intermediate cell units into an upper cathode compartment containing an 'ionpermeable diaphragm supported by the cathode, and a lower anode compartment. The cathode compartments and the anode compartments have different outlets for the gaseous products and liquids removed from each compartment.

10 Claims, 2 Drawing Figures PATENIFDNUV 81875 & M EDO CHA RLES ,BA RNA BE INVENTOR ATTORNEY MULTIPLE TIER HORIZONTAL DTAPHRAGM CELLS This invention relates to a multiple tier horizontal diaphragm type electrolytic cell series useful for the production of chlorine and caustic.

A well-known method of producing chlorine is by the electrolysis of the chloride of an alkali metal, e.g., sodium chloride in an aqueous solution in an electrolytic cell containing a diaphragm separating the anode compartment from the cathode compartment, collecting the chlorine at the anode and hydrogen and a solution containing the corresponding alkali hydroxide, e.g., sodium hydroxide, at the cathode.

Horizontal diaphragm cells are known to the art, for example, J. Billiter, Die Technische Elektrolyse der Nichtmetalle, Vienna, Springer-Verlag, 1954, pp. 242-25 1. It is also known to form multiple tier mercury cell units as illustrated by U.S. Pat. Nos. 2,719,117 and 3,308,047.

Generally, it is an object of the present invention to provide an unique cell series for producing chlorine and alkali metal hydroxides by the electrolysis of brines comprising the corresponding ions.

Another object of the invention is to provide a multiple tier, horizontal diaphragm cell series construction made up of a top compartment, a plurality of intermediate cell units of essentially similar construction whereby multiple tier horizontal diaphragm cell series of any desired height or number of cell units may be readily built up, and a bottom compartment.

Another object of the invention is to provide a multiple tier horizontal diaphragm cell series which is constructed in part from a horizontal mercury cell whereby the advantages of high current density and low voltage coefficient attainable in the operation of a mercury cell are combined with the lower decomposition voltage attainable in the diaphragm cell and in addition, avoid polluting natural resources with mercury.

The electrolytic cell of the present invention for producing chlorine and alkali metal hydroxide comprises a multipletier horizontal diaphragm cell series comprising a top anode compartment having anodes therein; a bottom cathode compartment having a cathode therein; a base supporting said cell series; and between said top anode compartment and said bottom cathode compartment at least one intermediate cell unit providing a pair of alternating cathode and anode compartments; each said intermediate cell unit having a horizontal, impervious partition dividing said cell unit into an upper cathode compartment and a lower anode compartment; a cathode having an ion-permeable diaphragm attached to the upper surface thereof; said cathode and said diaphragm being positioned between each pair of adjacent cell units and defining a cathode compartment between said diaphragm and the partition below and an anode compartment between said diaphragm and the partition above; anodes electrically connected to and supported below each said partition in said anode compartment; electrically conductive supports in each cathodecompartment connecting each said cathode with said partition below; an electrical supply line to the anodes in said top anode compartment and to the cathode in said bottom cathode compartment; and inlets for introducing electrolytes in each of said anode compartments and outlets for removing products therefrom.

The invention comprises apparatus for electrolyzing conductive solutions which comprises a series of cell units. A self-supporting top compartment is over the uppermost cell unit, and supports the anodes for this uppermost cell unit. Anode compartments contain a plurality of inlets for the introduction of the electrolyte and outlets for the removal of the electrolyte and the removal of gaseous products.

The top compartment is preferably constructed of a chlorine-resistant material, for example, rubber covered steel, concrete, or polyvinyl chloride.

An ion-permeable diaphragm separates the anode compartment from the cathode compartment and is supported by the cathode.

Cathode compartments contain cathodes structurally supported by vertical electroconductive supports and attached to the side walls. Cathodes are positioned horizontally along the underside of the diaphragms. The vertical supports also serve as electrical conductors connecting the cathode in each cell unit in series with the anode in the next lower cell unit. Cathode compartments contain suitable outlets for removal of liquid and gaseous products.

Partitions are used to isolate each of the cell units in a multiple tier cell series. In addition to constituting the bottoms of the cathode compartments, they serve as anode supports for anodes in the next lower cell unit. The partitions are positioned by being attached to the walls of the cell unit. They may be sloped to accommodate separation of liquid and gases in the anode and cathode compartments.

Partitions are suitably'constructed in the form of, for example, plates or sheets. Suitable materials of construction are, for example, steel or clad metals, for example titanium clad steel.

Anode assemblies suitable for the patent invention are, for example, described in U.S. Pat. Nos. 3,140,991 and 3,260,662. While graphite anodes are suitably used in the top-anode compartment, metal anodes are preferably used in all anode compartments because of their dimensional stability. Metal anodes are those of a metallic base for example titanium, tantalum, copper, nickel, magnetite, iron, and alloys thereof, where at least part of the metallic base. is coated with a chlorine resistant, electroconductive coating. Particularly suitable are, for example, anodes of titanium having a thin coating over at least part of its surface of a platinum metal or oxide. By the term platinum metal is meant an element of the group consisting of ruthenium, rhodium, palladium, osmium, iridium and platinum and alloys of two or more of these metals. The term titanium is meant to include alloys essentially of titanium.

Cathodes are suitably constructed of, for example, iron, stainless steel, or platinized titanium and in the form of a grid, perforated sheet metal, expanded mesh, or screen. The preferred cathode of this invention is a steel grid.

Vertical electroconductive supports are suitably constructed of, for example, steel, copper, aluminum or clad metal.

Fluid permeable diaphragms constructed of a halogen-resistant material, for example, asbestos or synthetic fibers, are suitable. Other type diaphragm materials are equally readily adaptable as will be apparent to those skilled in the art. While diaphragms used on cathode members may be pulled from an asbestos slurry by the use of suction in a conventional manner,

the flat surface of the cathode grid permits the use of diaphragm fabrics in cells of the type of this invention. Utilization of diaphragm fabrics instead of deposited diaphragms allows for controlled diaphragm thickness throughout the cell. Attachment of the diaphragm to the cathode grid is accomplished by any suitable mechanical means for example, mounting clips, clamps, adhesives and the like. The diaphragms are preferably one-sixteenth to one-eighth inch thick to electrically separate the anode compartment from the cathode compartment. Removable diaphragm-cathode grid units are suitably used to facilitate changing of diaphragms.

An important objective of the present invention is the conversion of horizontal mercury cells to horizontal diaphragm cells. Mercury cells such as the Olin E-510 cell, earlier called El 1, or 13-812 cell [Chem. Engineering Progress 59, No. 4, 77-80 (1963); Chem. Week Sept. 28, 1968, pp. 74-5; Chem. Engineering Progress 61, No. 3, 94109 (1965) may be incorporated into the horizontal diaphragm cell series of this invention by removing the cover or top compartment of the mercury cell and using this as the top compartment of the uppermost cell unit of the present invention. This top compartment includes anode supports, anodes, apparatus for anode adjustment, for example, jacking screws, and electrical connections for the anodes. Detailed illustrations of one example of this top compartment are given in US. Pat. No. 3,140,991 as well as in Chem. Engineering Progress 59, No.4, 77-80 (1963). Other types of horizontal mercury cells can also be advantageously converted to the cells of this invention.

The cathode compartment of the mercury cell is used as part of the bottom compartment of the lowermost cell unit.

Introduction of a plurality of intermediate cell units of this invention below the top compartment of the uppermost cell unit and above the bottom compartment of the lowermost cell unit completes the multiple tier horizontal diaphragm cell series structure of this invention.

The horizontal diaphragm cell series of the present invention permits the use of high cathode current densities normally associated with mercury cells. Using metal anodes, for example, titanium having a thin coating of a platinum metal or oxide, cathode current densities from about 3.0 to about 6.4 amps/in. are attainable whereas the normal current density of a diaphragm cell is about 0.7 to about 1.5 amps/in. Lower decomposition voltages associated with the operation of diaphragm cells are also attainable with the cell of this invention. Thus the initial decomposition voltage for a diaphragm cell of 2.3 volts can be coupled with the lower voltage factor of 0.15-0.26 associated with mercury cells to provide lower operating voltages. Voltage factor values for a number of commercial cells are given in Chemical Engineer, CE 55, March, 1968.

FIG. 1 shows the structure of a multiple tier horizontal diaphragm cell series in accordance with the present invention. Inlet 1 introduces brine into anode compartment 2. Anode support 3 is a combination copper bus bar and anode support and introduces current to the cell. Anode support 3 is drilled with holes at suitable spacings to receive anode lead-ins 5 and jacking screws 6.

Current flows from anodes 18 through the brine to cathode 13. Vertical electroconductive supports 4 electrically connect in series cathode 13 with partition 17 and anode supports 20 of the intermediate cell units.

Top 7 of anode compartment 2 is drilled with holes at suitable spacings to receive anode lead-ins 5. Anode 18 for the uppermost cell unit is suspended from anode support 3 by lower lead-in nut 8 and upper lead-in nut 9 both threaded on lead-ins 5 and together locking the anode assembly.

Outlets 10 are provided to remove chlorine produced during electrolysis from anode compartments 2. Outlets 11 are provided to remove spent brine. Spent brine can suitably be recirculated to obtain optimum cell voltage. The upperside of cathode grid 13 supports diaphragm 12. Cell liquor percolates or flows thru the diaphragms and is subjected to further electrolysis within cathode compartment 14.

Outlet 15 removes hydrogen liberated at cathode 13. Outlet 16 removes caustic soda produced through seal legs (not shown) to prevent air leakage into cathode compartment 14.

Partition 17 forms the bottom of the cathode compartments and the top of the anode compartments for the cell unit immediately below. Lower surface 19 is composed of a corrosion resistant material, for example, rubber or titanium-plated steel.

A plurality of anode supports 20 project downwardly from the lower surface 19 of partition 17. Anode supports 20 may form an integral part of partition 17 or may be secured to it by attachment means. Anodes 21 are secured by attachment means to the lower end of anode supports 20. A non-conducting material, for example, rubber, covers anode supports 20.

Bottom compartment 29 is constructed of a conducting material, for example, a steel base supported by concrete and serves as the foundation for the multiple cell unit. Cathode bus bar 30 is attached to the conducting surface of bottom compartment 29 and completes the electrical circuit.

FIG. 2 shows an example of suitable insulating means for connecting cell units for this invention. It is important that each cell unit be electrically insulated from the adjacent cell units.

Side channel 24 of the uppermost cell unit is secured to side channel 27 of an intermediate cell unit by bolt 22 and nut 28 extending through the flanges of the side channels. Side channel 24 is lined with a nonconductive coating 25, for example, hard rubber. Diaphragm 12 serves as a non-conductive insulating layer between the flanges of side channel 24 and cathode l3. Insulating bushings 23 insulate bolt 22 from side channel 24, and side channel 27.

While a preferred embodiment of a two cell unit of the improved multiple tier horizontal diaphragm cell has been illustrated and described, it will be understood that various modifications and changes may be made without departing from the spirit of my invention or the scope of the following claims.

What is claimed is: I

l. A multiple tier horizontal diaphragm cell series comprising a top anode compartment having anodes therein, a bottom cathode compartment having a cathode therein; a base supporting said cell series; and between said top anode compartment and said bottom cathode compartment at least one intermediate cell unit providing a pair of alternating cathode and anode compartments; each said intermediate cell unit having a horizontal, impervious metal partition dividing said cell unit into an upper cathode compartment and a lower anode compartment; a cathode having an ionpermeable diaphragm attached to the upper surface thereof; said cathode and said diaphragm being positioned between each pair of adjacent cell units and defining a cathode compartment between said diaphragm and the partition below and an anode compartment between said diaphragm and the partition above; said anodes electrically connected to and supported below each said partition in said anode compartment; electrically conductive supports in each cathode compartment connecting each said cathode with said partition below; an electrical supply line to the anodes in said top anode compartment and to the cathode in said bottom cathode compartment; and inlets for introducing electrolytes in each of said anode compartments, liquid outlets for removing liquids from said anode compartments and said cathode compartments and separate gas outlets for removing gaseous products from said anode compartments and said cathode compartments said liquid outlets being different from said gas outlets.

2. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which said cathodes have the form of a steel grid.

3. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which said cathodes have the form of a perforated metal sheet.

4. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which said cathodes have the form of an expanded metal mesh.

5. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which said anodes in said top anode compartment are graphite.

6. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which said anodes in said top anode compartment are a metallic base coated over at least part of its surface with a platinum group metal or oxide thereof.

7. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which all said anodes in said anode compartments of said intermediate cell units are a metallic base coated over at least part of its surface with a platinum group metal or oxide thereof.

8. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which all said anodes in said anode compartments are titanium coated over at least part of its surface with a platinum group metal or oxide thereof. I

9. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which said electrically conductive supports are steel.

10. A multiple tier horizontal diaphragm cell series of claim 1 in which each of said cell units is secured to the adjacent cell unit by a detachable insulated connection. 

2. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which said cathodes have the form of a steel grid.
 3. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which said cathOdes have the form of a perforated metal sheet.
 4. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which said cathodes have the form of an expanded metal mesh.
 5. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which said anodes in said top anode compartment are graphite.
 6. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which said anodes in said top anode compartment are a metallic base coated over at least part of its surface with a platinum group metal or oxide thereof.
 7. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which all said anodes in said anode compartments of said intermediate cell units are a metallic base coated over at least part of its surface with a platinum group metal or oxide thereof.
 8. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which all said anodes in said anode compartments are titanium coated over at least part of its surface with a platinum group metal or oxide thereof.
 9. A multiple tier horizontal diaphragm cell series as claimed in claim 1 in which said electrically conductive supports are steel.
 10. A multiple tier horizontal diaphragm cell series of claim 1 in which each of said cell units is secured to the adjacent cell unit by a detachable insulated connection. 